Shamed by his failure to protect the humans and abandoning his men, he wandered the wilds of Lordaeron before being contacted by an ambassador of the Kul Tiras with the prospect of regaining his honor.

Dagren may have been killed by Samuro to get an Orb of Lightning, although he doesn't need to be slain for the quest to be completed. He failed to slay the blademaster and was massacred along with his men when a group of naga wiped out the entire garrison.[2]

Dagren died trying to prove to himself and the world that he was a great hero, when he already was one.